The present invention relates to an output level controlling apparatus in an apparatus for reproducing recorded information, and more particularly to an improvement in an output level controlling apparatus for controlling the reproduced output level of a reproduced digital signal by means of a digital attenuator.
For example, a compact disk (CD) is sometimes used as a music source for background music (BGM), and a plurality of compact disks CD are sometimes loaded in an automatic player in which the compact disks CD are continuously played to produce BGM.
In such cases, since the reproduced output levels of compact disks depend upon the recording conditions and the like of the disks and are thus different from each other, if an acoustic signal is output by continuously reproducing a plurality of compact disks, the output level sometimes suddenly increases or conversely suddenly decreases at each time the compact disk played is replaced by a new disk. In addition, when the pieces of music in the same compact disk are continuously played, the pieces of music have different output levels, the same variations as those described above occur in the output level. This defeats the purpose of BGM to form, as background music, a comfortable music environment. In order to prevent such a problem, it is though that a sudden change in an output level is restrained by keeping the output level of music within a predetermined region.
In an example of such control means, the peak value of each of the signal levels of the information recorded on all compact disks (for example, 6 disks) loaded in an automatic player may be previously read, and the read peak values may be matched to the lowest peak value. However, in this control means, since all compact disks must be reproduced for reading the peak value of each of the signals, a certain time is required for preparation before BGM playing.
The inventors thus proposed an output level controlling apparatus in a feedforward system in which an appropriate output level for BGM is previously statistically determined to produce a reference value of output levels, and an actual output level is compared with the reference value so that the appropriate output level is maintained by controlling a digital attenuator in accordance with the reproduced output level of the reading/recording signal with the results of comparison (Japanese Patent Laid-Open No. 1-231510). Since this apparatus employs the feedforward system, no time is required for preparation.
However, in the above-described conventional means, when a signal level is either attenuated or increased, the output level changes to a value above and below the reference value in the vicinity thereof because the changing time and changing amount of the signal level are constant, and aural sound vibrations, i.e., a feel of instability, thus occurs.
It is considered that such sound vibrations can be removed by setting a time for changing a level to be long.
However, when the time for changing a level is set to be long, if a high level is input, the level cannot be momentarily attenuated. This is undesirable because the output level, i.e., loudness is increased, and the music environment of BGM is thus destroyed.
In BGM, plural pieces of music or a plurality of record media are continuously reproduced. When a piece of music is continuously reproduced while maintaining the attenuation amount of the prior piece of music, for example, if the level of the music to be reproduced is low, the starting portion of the music cannot be heard.